I've had ongoing cooling issues on the highway. Airdam in tact and no blockages. On the highway I nearly reached 3/4 on temp. I was past 220. I pulled over and turned on the heat. This was with ac on. Kept driving once it cooled to 220 and it would slowly heat up again. Once I got home I popped the hood and coolant started coming out of the overflow. Brand new cooling system. If not a head gasket, possible thermostat?

It drove just fine and wasn't sluggish. It cools wayyyy down on in town driving. No bad driving issues in town either hot or cold. Today was especially hot too around 100 degrees.

As I said in the other topic I am an EMT and need my vehicle for response to the station when there's a call so I need to try and keep its downtime low so I want to start with the thermostat.

Any advice is greatly appreciated

 

Also I forgot to add that I don't believe the temp sensor is bad because I get bad gas mileage as soon as it starts getting hotter

 

Sounds like a "dye test" (or other test) for combustion in the coolant is in order. This to look for head gasket, cracked head problem.

Last time I was hurting for a reliable car, I leased a 2016 Chev Cruze for $92 mo. w/ $1000 down, to alleviate the stress. (There now running a little more).

 

try a new radiator cap before going further.

then let it idle in the driveway. it should heat up until the fan comes on, cool down until the fan turns off then repeat until it runs out of gas

 

I will try a new cap asap!
The car does just fine idling by the way. I sat outside in the heat with ac waiting on a friend and it barely touched middle and went down. In town it is fine around 30 or so. But when you start holding rpms like highway or even about 45-50 it starts having some issues

Once I try the rad cap I will do a compression test. Been holding off because I don't want to know if it is a head gasket or not lol. I've only done a compression for leaks, how would I do one for a head gasket?

 

Unfortunately I haven't had a break to do any work. I did notice tonight this vacuum line was unhooked. Also when the car gets over half the overfill goes all the way to the top and stops?


Unhooked line




The round portion on top is where it connected to

UPDATE: Purchased a 160 degree fail safe - says when it overheats it stays open permitting coolant flow which i suspect may be my issue.
Purchased the gasket. As well as some strong coolant. Anyone remove the tstat on tpi without removing the intake? My problem has got worse as it will overheat during idle. No coolant in oil or vice versa

 

Pulled over when I started to overheat and the fan was not on. This explains in town overheating, but on the highway?

 

Is your air deflector in place?? if that's not there,that would cause the overheating while your driving!.

 

Yes sir. I actually reenforced it too just to be sure!

 

a different t-stat won't solve an overheat issue unless the old one is stuck closed.

try a radiator cap first

fix your fan

 

I wanted to replace the thermostat because the car got really hot and I'm afraid it may be stuck causing a partial issues

The radiator cap didn't fix it sadly. The fan is under warranty. Had to respond in bad weather and I think some water messed it up

 

Will have an answer tomorrow if the fan fixes all of it. Would a bad cooling fan cause the ac to get warm at idle?

 

Absolutely yes. Those fans need to be on to get reasonable A/C performance. With no fan(s) running, the A/C is going to perform very badly.

 

Update
Fan was replaced, motor was bad. Didn't turn on because relay was burned out and the pigtail wires were frayed and shorted

 

Glad you found the problem.

 

My lingering question is highway overheats. Does the fan come on if ac is on while on the highway. I read here that the fan cuts off over 40. Didn't know if having the ac on meant it runs constantly

 

for an 86 the fan is likely engaged by a switch within the AC head and runs continuously while the AC is on.

running on the highway won't hurt it

 

Perfect, that was my concern because of my bad highway overheat

 

^^^^

 

Well the repair continues.

The relay, new fan motor and pigtail still does not activate the fan to come on. What else could be missing?

 

Did you ever change your Coolant Temp.Switch ?

 

Not yet, I assumed since it doesn't come on when the ac comes on something in the circuit is wrong

 

http://contentinfo.autozone.com/znet.../TU66/image/2/
You almost replaced everything else,I would change the AC pressure switch and the coolant temperature switch for now there's nothing else left to change,unless you got a bad fan motor from your supplier.
This would drive me

 

I believe the shop that put it in said when they manually powered it, it came on but I will double check. Anyway to temporarily have it come on when the cars on? I read about grounding it to another circuit but I don't have any idea which wire to ground or where to ground it. This will help since I need a quick fix and I drive with ac all day anyway so the fan would normally be running until I have more diagnosis time

 

No, I don't were to ground it either. Me personally, I would take the car to my mechanic for something like that.

 

Sadly this entire week its been at my mechanic. They've had a hell of a time. They replaced the blown relay and wiring. I got it back today because this unfortunatly is the last day this month I can take off. So hopefully I can figure out a fix

 

Just so we are all on the same page:
Relay, fan motor, and pigtail was replaced.

Fans do not come on period, even if ac is on. Mechanic said all wires and fuses are getting power but it isn't starting the fan but they can jump the fan? Any fuse I can check. I checked the relay connector. Looks all okay. Not sure how to pull the wires out of the connector to ground green and white wire

 

i'd change the coolant temp sensor/switch as suggested.

if that doesnt work, maybe a kit like this would work for ya?
https://www.summitracing.com/parts/der-16759/overview/

 

Check the power to and from the HVAC head. There is a switch in there that goes bad as it is a rotating contact switch. This is what sends the power to the fan relay when you turn on the a/c. this just controls the a/c part.

 

Changed coolant temp and fan switches. No change, where is the fusible link located?

 

IIRC,it's the thin Red wire coming off the battery terminal,There's the big red wire(starter) and a Black and Red wire that goes to some sort of junction.feel if the red wire has a break in it right after the junction.(This is all in the battery area.)
it should be just under where the ground cable is in this pic,

 

Hmm that's the part they replaced. Looks like I need to double check the wiring diagram to see what else may be causing an issue

 

Did you put that 165 stat in? How many fans do you have. Mine is a 90 and has 2 fans. The primary is activated by the ecm. The ecm has programmed parameters that keeps it from turning on the primary fan until it hits 195 degrees. So if you put a lower temp tstat in, your primary fan still won't kick on till 195. If you did put the lower temp in. Was it before you changed the temp sensor? Also if you do have a secondary fan, what temp is the sensor on that. Stock doesn't come on til like 245 I think.

 

No the original t stat is still in it. And it is an 86 with single fan. From what I remember the fan came on around 220. It got up to 240 the other day and nothing

 

I wonder how it's wired. I hate adding toggle switches..... Maybe flushing the system..... Maybe your ecm needs more than the information it gets from just the coolant temp sensor which is different than the coolant temp sending unit. But your fan has it's own sensor which is not controlled by the ecm. Ecu. Sorry. If the fan is wired correctly, it has it's own sensor. If that doesn't make it turn on, I'm not sure. Unless if it has it's own sensor but it's wired to your computer and that makes it fail???
I'll do some digging. At least you can drive it for now. Good luck!!!!!

 

I do have a update. Checked relay today with car running and ac on. The relay was grounded because I got sparks on the ground wire. I had no power from any of the other terminals. I believe there is three to four pins. In any regard, one is empty. None had power but it was grounded. I tested these by pulling the terminal from the relay checking the pins

 

Turns out the computer wasn't supplying ground. So I grounded it when the car comes on

 

My 86 Iroc has been having some overheating issues. I just replaced the radiator with an aluminum 3 core and the thermostat as well. I drive the car for 30 minutes and it's fine, but then it starts to overheat and builds up pressure pushing water into the overflow tank.